There are many cases where a telephone call suddenly rings or someone suddenly comes while the user is enjoying a television broadcasting program, so that he overlooks a broadcasting program. If the user overlooked a television broadcasting, this program can never be seen except for a program that is rebroadcasted. It is a rare case that the program is rebroadcasted in a short period of time. A news program and a sports program are not rebroadcasted in most cases. In many cases, therefore, if the user overlooked a television broadcasting program, this program cannot be seen forever.
There is a case where a scene such as good scene of a movie or a drama, interview of an important person, highlight scene of a sports program, or the like which the user wants to preserve suddenly starts during the watching of a broadcasting program. In such a case, even if the user immediately sets a VTR, he misses such a scene and he often cannot record the scene.
Therefore, a television receiver such that while the user is watching a broadcasting program, such a program is always recorded on a recording medium is considered. In such a television receiver, even if there is a sudden telephone call or someone suddenly comes, such a program can be traced back and reproduced and he does not overlook the program. Such a program can be easily preserved and even if a program which the user wants to record suddenly starts, it is possible to cope with it.
As a recording medium in the television receiver such that a program is always recorded onto a recording medium as mentioned above, a hard disk drive can be used. Hitherto, as a recording medium for recording a video signal, a magnetic tape is widely used. However, an accessing speed of the magnetic tape is slow and it is difficult to use it as a recording medium that is used in such a television receiver. Although the use of a semiconductor memory is considered, the semiconductor memory of a large capacity is very expensive. In the semiconductor memory, if a power source is turned off, the preserved program is erased, so that it is inconvenient in case of preserving a program for a long time. On the other hand, in the hard disk drive, a capacity is large and an accessing speed is also high enough.
In such a television receiver in which a program is always recorded on the recording medium, a video signal based on a received television broadcasting radio wave is converted to a digital video/audio signal, is compression encoded by a predetermined method, and is recorded to a hard disk drive. For example, a motion JPEG is used for the compression encoding of video data. An audio signal is also converted to digital data by a predetermined method, is compression encoded, and is recorded.
FIG. 12 shows an example of the operation of a television receiver such that a program is always recorded to a recording medium. A television broadcasting as shown in FIG. 12A is received by a tuner. Hereinlater, the television broadcasting which is received by the tuner is called a real-time broadcasting and is distinguished from a video image by the television broadcasting which is reproduced from a hard disk drive. The received signal is subjected to processes as mentioned above and is always written and recorded to the hard disk drive in a real-time manner.
A case where there is an overlooked scene during the watching of a real-time broadcasting by the user and the overlooked scene is reproduced by a predetermined method, for instance, an instruction from a remote commander will now be considered. For instance, in FIG. 12, an instruction to reproduce the overlooked scene is issued from the user to the television receiver at a time point A of the end of an interval a2. In the television receiver, thus, compression data in an interval between a0 and a2 is read out from the hard disk drive while tracing back by only a preset time t0 from time point A when the instruction is issued. The read-out compression data is sequentially subjected to predetermined processes such as compressing and decompressing processes and the like and becomes a reproduction video/audio signal which is started from time point A (FIG. 12B). The timing to start the reproduction video/audio signal is actually accompanied with a slight delay due to the relation of the signal processes.
As for the reproduction video/audio signal obtained as mentioned above, the video signal is reproduced by a video monitor of the television receiver and the audio signal is reproduced by a speaker. The reproduction video/audio signals in the interval between a0 and a2 which was read out from the hard disk drive are reproduced from time point A as shown in FIG. 12C. In this example, it is rewritten to an interval between a3 and a5 of the real-time broadcasting and is reproduced. When the reproduction of the interval between a0 and a2 is finished, the monitor video image and the speaker sound are returned to those by the real-time broadcasting.
However, in the television receiver such that the program is always recorded to the recording medium, when the compression data recorded in the hard disk drive is reproduced by tracing back from the present time, it is merely traced back by time t0 which has previously been designated. There is, consequently, a problem such that it is impossible to return to an arbitrary scene which the user wants to see and reproduce it. That is, for example, in FIG. 12, even in the case where the user wants to again watch the scene in only the interval a1 at time point A, there is a problem such that the program has to be reproduced from the interval a0.
There is also a problem such that even if the hard disk drive is provided, it is impossible to trace back while searching a scene which the user wants to see.
There is, further, a problem such that it is also impossible to wait for a video image of the real-time broadcasting in a still state (paused state). For instance, even in the case where the user leaves his seat for a little while, the reproduction cannot be started from the interrupted scene when he comes back.